Apparatus for determining ranges.



G. DAVIS.

APPARATUS FOR DETERMINING RANGES.

APPLICATION FILED MAR. 22, 1911.

1,063,862. Patented June 3, 1913.

[I lllllllll' awue'ntoz COLUMBIA I'LANnunAPH c0. WASHINGTON, u c,

CLELAND DAVIS, OF THE UNITED STATES NAVY.

APPARATUS FOR DETERMINING RANGES.

Specification of Letters Patent.

PatentedJuno2;. 19.13.

To a u /mmif may concern.

Be it known that l, Ccnmnn DAVIS, a citizen of the United States, lieutenant (one mander in the United States Navy and serving on board the U. S. S. ilf'issz'ssippi, have invented certain new and useful Improvements in Apparatus for Determining Ranges; and I do hereby declare the following to be a :tull, clear, and exact descriptionv ot the invention, such as will enable others skilled in the art to which it appertainsto make and use the same.

The present invention relates to a. method of and an apparatus for determining ranges and spotting the points of impact of projectiles and has for its object. to provide a means that will furnish an accurate picture to scale of the region surrounding the point at which a projectile strikes during gun fire, and which will also enable the operator to determine with accuracy trom this picture the distance between the target and the point ol striking of a projectile, the l'ieight ot the object fired at, as well as other data which will appear hereinafter.

To these ends the invention consists in the steps constitutiug my process, and the novel arrangement of parts more fully hereinafter disclosed and particularly pointed out in the claims.

te'terring to the accompanying drawings torining a part of this specification in which like numerals designate like parts in all the vicwszl igure l is a diagrainirnitic seetional view o'l an instrument comprising a camera built in accordance with my invention; Fig. 2 is a diagrammatic view 01 the picture taken by the came a and from which the various computations may be made; Fig. 3 is a detail view showing a pair ot the film guiding rollers; Fig. 4 illustrates a graduated range tinder scale; Fig. 5 illustrates a scale employed in ascertaining the height oil. the object fired at; and Fig. 6 illustrates a scale employed for determining the distance of the object when the height has been measured on the picture by the scale shown in Fig. 5.

in. the present state of the art of naval gunnery the main ditlienlty experienced by gunnery otlicers is due to the lack of means tor ,determining the range of the target with sutlicient accuracy to obtain a correct elevation of the sight bar on the gun being fired. According to present methods, the range of the target is found from -ange finders having a limited base and the inaccuracies oi these instruments are well known. (iunuery ollicers, therefore, do not wholly rely upon them as a means of obtaining an accurate sight bar range in elevating the guns, but instead they consider the distances so obtained as merely approximations that give a basis, so to speak. from which, by observing the splash and estimating its distance trom the target, the necessary correction can be applied to the sight bar height to bring the next projectile to the target.

As is well known, it is the duty ot the spotter to estimate this correction. lie is stationed alo'tt and by th: aid of glasses estimates with his eye the distance the projectile strikes over or short o't the target and then communiiaites the eorres])onding sight bar correction to the sight setters at the guns. But it is recognized that these methods are unproductive ot results com-- mensurate with the accuracy ol the guns, not only lor want of accurate and reliable range finders, but also because personal er rors are involved, and lurther, the human eye is not adapted to the measurement of distances, so that the spotter's cm'rections are, in tact, hardly more than good guesses.

My invention obviates the above objec tions by making use of a camera having an objective ol a known focal length, which therefore produces a permanent picture to scale ol the relative positions of the horizon, the target, and the splash, and than which all the necessary data required by the gunner may be accurately determined, as will now appear.

.1, indicates the object glass of any suitable camera having a known focal length 2, and provided with a sensitive surface 3 on which is produced an image at of a size propmtional to the object photographed, and this sur- 'tace or film is passed through a developing lluid 5 over a pair of rollers (3, through a washing fluid 7, over a pair of rollers 8, through a fixing solution 9 and past the magnifying lenses 10 carried by the camera on to the winding reel it, as shown. Of course, any other suitable arrangenicnt ot the sensitized surface may be employed if desired.

A scale 12 is mounted within the focus of the lens 10 and is graduated in accordance with the angles subtelnled between the object tired at and the horizon for a given height above the water line, and for the fixed focal distance 2 of the lens 1. In other words, since the points of graduation of the scale 12 correspond to the angles subtended by the horizon and water line of the vessel being fired at, they may, therefore, be made to correspond to the distances between said water line and the ()bStlYGl', as will be clear to those familiar with Buckners method of determining distances at sea.

The camera being located for example, in the top of a vessel and at the distance above the water line corresponding to that for which the scale 12 is graduated, is then sighted upon the object by the aid of the finder telescope 13. The target being brought into the field of the camera, the picture is then taken in the usual way, is de veloped, fixed and then brought into the focus of the magnifying or observing glass 10, as will be readily understood. Now, since the scale 12 is graduated for distances corresponding to the angle subtended by the object and horizon, as above stated, if the horizon line H of the said scale is made by means of a micrometer screw, not illustrated, to coincide with the horizon line 14c on the picture, the distance H P on the scale 12 be tween the said horizon line 1 1- and the water line 15 of the ship being fired at will give the distance of the said ship from the point of observation. The distance of the ship being fired at having been obtained, in the manner described, it is used as a sight bar range for the guns. Upon firing, however, the splash 10 of the projectile will be plainly visible in the vicinity of the target and another picture is taken which will include as before the horizon line 14, the water line 15, and in addition, the splash 16. Proceeding as before, this picture is now brought into focus of the magnifying glass 10, the scale 12 is applied and the distance P Q on said scale corresponding to the amount the shot falls short of or falls beyond the target is noted. In other words, the second picture upon a comparison of the range given by the sight bar with the real range as given by the scale 12, gives at once the ballistic error of the gun. It follows that for the next shotthe necessary correction may then be applied to the sight bar range which will immediately bring the gun on the target. When the distance of the target is known, the point of impact of a projectile may be determined by placing the graduation corresponding to that distance on the water line of the target, then the mark on the scale which coincides with the splash will give the distance of the point of fall.

It sometimes may happen that the horizon 14- of the sea is invisible, while the water line 15 of the ship 17 is visible. In such case, the distance of the target or ship may be estimated by any of the well known means now in use aboard ship, and the splash noted as before. Then upon observing the distance P Q between the splash and the ship fired at, the sight bar reading is corrected for such distance, whereupon if the target is not struck, the operation is repeated until the distance between the splash and the target is eliminated and a shot is observed to reach the target. Or, the range correspond-- ing to the sight bar height may be used a point of reference, the mark on the scale corresponding to this height being made coincident with the splash, when the graduation coincident with the water line of the target.- will give the approximate distance of the target. It will thus be seen by the simple expedient of producing a picture to scale showing the relative positions of the horizon, the water line of the target and the splash of the projectile, and by taking measurements from this picture, I am enabled to accurately determine all the necessary data for accurate firing.

As above stated, however, not only does the distance of the horizon bear a fixed relation to the height of the image with a given focal length of lens, but when the distance of the target, the height of the image and the focal distance of the lens are all known, the height of the target be obtained. That is to say, to determine the height 18 of the point 19 from the water line 15, the distance of said water line from the point of observation having been found as above described, the scale 12 is withdrawn from the focus of the lens 10, and the scale 21 is substituted therefor. This latter scale is graduated in suitable units. and. the height is obtained from the formula Height of object Distance of object Height of image Focal length of lens From the height thus obtained, by the aid of the scale 22, the distance of the object may be readily determined, when the horizon is not visible.

The scale 22 is graduated as follows Starting at any distance from. the point of observation say 2000 yards, the line 23 of the scale 22 is drawn of that length which the known height of a target would occupy in the picture on the film 3. Then the next division 24 of the scale 22 would be drawn of a length to represent the same height of the target at a range of say 2500 yards, and the next line 25 to represent the same height of target at a distance of say 3000 yards, and so on until the line 26 might represent the height, of the same target at a distance of 8000 yards. The object in obtaining the height 18 is to enable the range to be obtained by subsequent observations when the horizon is invisible or not clearly defined. It will also enable the range to be closely determined by observing with similar instruments located closer to the water line where r it is not practieal'ilt-i to measure the angle subtended between the horizon and the water line. The scale 22 correspomling to this height is inserttal in the locus of the eye-- piece 10. in place ot the scale til. the picture taken and the scale moved laterally until the height 19 is just included between the slant. line and the base line. The graduation on the base line at the bottom of the ordinate will thus indicate the range.

it will be noted that when the height method oF detern'lining the range is used, the instrument need not be mounted at a tixcd. height above the horizon. it is only necessary that the known heightot the target be included in the picture, for as the object approaches or recedes the height of the image increases or decreases proportionately, and the range is really determined by a similarity of triangle.

Other valuable uses of the instrument sug gest themselves. For example, by taking a series of observations at regular intervals the cours"v and speed of moving vessels may be readily iiletermined. Also since the instrument provides a picture to scale of (listant objects, light houses and other known objects on shore may be photographed and used as a basis for obtaining usetul data. The scales are made removable so that the instrument may be used either as a spotting instrument or to determine the distance ot an object at sea when the height is known. Thus the distance ol an object:- may be detern'iined by means of the Buckner scale or the actual. height of the object being known it can be used as a basis to determine its distance. A number of scales grat'luated :tor dit't'erent heights are provided.

It is obvious that those skilled in the art may vary the details of (:(mstruction and the arrangement of parts as well as the steps of the method disclosed without departing from the spirit of my invention, and therefore I do not wish to be limited to the disclosure above, except as may be required by the claims.

What I claim is 1.. In a distance instrument the combinatioii ol a camera adapted when located at a known distance above the plane of the horizon to make a picture of said horizon and an object having an unknown height; and a plurality of scales graduated in accordance with said distance and height adapted to determine by the aid o't said picture the real distance and height of said object, substantially as described.

3. In a distance instrument. the combination of a camera adapted to make a photograph ot' an object and the horizon from a position at a known distance above the horizon; a scale graduated to said distance adapted to measure in terms ot the real range the distance between said object and horizon on said picture; and means for magni'tying said wale aml picture, substantially as described.

2). In a distance instrument, the (,Olllbllltttion of a camera adapted when located at a known distance above the plane of the horizon to make a picture of said horizon and an object: having an unknown height; a plurality of scales graduated in accordance with said distance and height adapted to determine by the aid ot said picture the real distance and height ol said object; and means For magni tying said scales and picture, substantially as ('lescribcd.

l. In a distance instrument, the conihina tion ot' a camera adapted when located at a known distance above the plane ot the horizcn to make a picture of said horizon and an object having an unknown height; means for immediately develo 'iing and lixing said picture associated with said camera; and a plurality of scales graduated in accordance with said distance and height adapted to determine by the aid of said picture the real distance and height of said object, substantially as described.

In testimony wherco't', I: atlix my signa ture, in presence of two witnesses.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

